A shoelace fits an upper to a foot. The upper fitted to the foot supports the foot. In view of this, a flexible member covering the instep is often provided with a reinforcement member.
However, the foot substantially changes its shape when dorsiflexed at the MP joint, and gaps are likely to occur between the shoe and the foot during movement.
As the posture changes, the shape substantially changes over an area from the MP joint to the middle foot section of the foot. If the upper, which is fitted to the foot when standing still, fails to follow changes of the shape of the foot, the fit between the upper and the foot significantly deteriorates during movement. Particularly, the reinforcement member has a greater rigidity than the flexible member, and is therefore less likely to follow changes than the flexible member.